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Re: Fwd: Gliders to Fliers? (Was Re: Ruben Strikes Back)



>Date: Sat, 25 Sep 1999 17:20:03 -0700
>From: dbensen <dbensen@gotnet.net>
>To: sarima@ix.netcom.com, dinosaur@usc.edu
>Subject: Re: Fwd: Gliders to Fliers? (Was Re: Ruben Strikes Back)
>Message-ID: <37ED66B2.806BC850@gotnet.net>

>>>I suspect that this, by itself, is why humans are bipedal, and *maybe*
>kangaroos as well (there *are* tree kangaroos after all).  That is, I
>suspect that this sort of tree-climbing decouples the limbs, and promotes a
>tendency towards bipedal locomotion on the ground.  Flight, or even
>gliding, is not really necessary to achieve this result.<<
>NOOOOO!  Well, I don't know about tree kangaroos and the climbing
hypothesis
>makes sense, but humans did not become bipedal as an adaptation to
arborality.
>Humans became bipedal AFTER they descended from the trees.  According to
>Steven
>Jay Gould ( I don't remember which article).  The mutation that lead to
many
>human characteristics (large head, straitened spine, etc.) were a mutation
on a
>gene that controlled ageing and also happened to alter leg development.
>Serendipitously, the new bipedal stance of humans left the hands free to
>manipulate things, and let humans rear up to gaze of the grassland (as Ray
>Stanford would say, 'like scared bunnies').  To some extent, humans are
>neotonous
>apes.

I dunno. Seems to me that bipedality results from a biological necessity for
the use of the hands for some other purpose than locomotion on the ground.
Perhaps for procuring food while in the trees (as in apes), to be enhanced
upon by humanoids using tools. Here at least is a mechanism for natural
selection to operate upon in a gradual manner. In the case of birds, the
necessity for greater flight maneuverability probably led to the rise of
bipedality.

What would be the case for Theropods (if one assumes they
evolved at first on the ground)? Most of them have relatively short arms.
Were the hands once so  usefull as to cause the evolution of the bipedal
stance?...and then degenerated later??? Or rather were they just vestiges of
once useful wings?